Motor vehicles typically include a drive train with a primary drive, such as an internal combustion engine, which is paired with a transmission in order to provide different gear drive ratios from the engine to the drive wheels. Typically, the transmission is connected to a differential which transmits torque from the transmission to output axles, with the differential compensating for different rotational speeds of wheels attached to the output axles which occurs, for example, during turning. Various transmissions are known including manual transmissions which include a vehicle operator activated clutch and a shifter which the vehicle operator uses to engage different gears, automatic transmissions which include internal clutches and speed sensors for automatic shifting between gears, double clutch standard transmissions which are electronically shifted based on various operating conditions, as well as continuously variable transmissions (CVTs) which offer a continuously variable torque ratio over a wide range of drive ratios without the need for separate gearing being engaged or disengaged as is required in the manual, automatic, and double clutch transmissions.
Differentials are also known in the form of both spur gear differentials and bevel gear differentials. Spur gear differentials provide an advantage in that the axial length of the differential in a direction of the output axes is drastically reduced in comparison to a bevel gear differential. Spur gear differentials utilize spur gears connected to a planetary gear carrier that itself is driven by the transmission output and drives the output axles via sun gears that engage the planetary gears. Here a first set of planet gears is associated with the first sun and a second set of planet gears is associated with the second sun, with the first and second planet gears also intermeshing via the first set of planet gears axially overlapping and engaging the second set of planet gears. The number of teeth of the planet gears of both sets is equal and the number of teeth of the first and second sun gears is also equal. Generally, the teeth of the first sun gear are arranged on a crown circle with a crown circle diameter that is different than the crown circle diameter of the crown circle on which the teeth of the second sun are arranged so that the first set of planet gears meshes with only the first sun and the second set of planet gears meshes only with the second sun. Such a spur gear differential is known from U.S. Pat. No. 8,480,532, which is owned by the assignee of the present invention and is incorporated herein by reference as if fully set forth.
Bevel gear differentials also include a carrier in which a pair of drive bevel gears are mounted that engage with a pair of driven bevel gears having a common axis that is arranged perpendicular to the common axis of the drive bevel gears. The driven bevel gears are connected to the output axels.
The inventor's prior U.S. application Ser. No. 14/923,886, filed Oct. 27, 2015, which is incorporated herein by reference as if fully set forth discusses a CVT differential that provides for reduced weight and the elimination of the need for a separate transmission in vehicles, and is particularly adaptable for hybrid motor vehicles.
For hybrid motor vehicles where a primary drive is provided, generally in a form of an internal combustion engine, and a secondary drive is provided, typically in the form of an electric motor driven via on board batteries in the motor vehicle, as well as for all electric vehicles that are only driven by electric motor(s), there is a continuing challenge to optimize the electric drive to conserve battery life and extend the vehicle drive range.